The balance of nutrient losses and gains in seagrass meadows

Abstract

Export of leaves and leaf fragments with currents, leaching losses from photosynthetically active leaves and from senescent and dead plant material, and nutrient transfer by mobile foraging animals, are processes specific to seagrass meadows. The nutrient losses are aggravated by denitrification and diffusion of nutrients from the sediments to the overlying water column. The persistence of most seagrass meadows points to an existing balance between nutrient losses and gains. Three processes may contribute to the replenishment of nutrients. Nitrogen-fixation undoubtedly is important, but continued biomass production requires other nutrients as well. Crucial contributions, therefore, must come from sedimentation and/or leaf uptake. The concept of the seagrass meadow as an open system, with nutrient fluxes from and to the system varying in time, allows for imbalances between nutrient losses and gains. These imbalances may contribute to fluctuations in annual seagrass biomass production. -from Authors